Sheet alignment apparatus and sheet finisher provided therewith

ABSTRACT

A sheet alignment apparatus includes: an aligning element for pushing a sheet supported on a sheet supporting face by moving in a direction perpendicular to a conveyance direction of the sheet, thereby aligning a position of the sheet; and a driving source for reciprocating the aligning element. An aligning face of the aligning element is arranged to be inclined with respect to the sheet supporting face.

This application is based on Japanese Patent Application No. 2005-206853 filed on Jul. 15, 2005, which is incorporated hereinto by reference.

BACKGROUND OF THE INVENTION

The present invention relates to a sheet alignment apparatus for aligning a sheet-like paper and a sheet finisher provided with the sheet alignment apparatus.

For paper with an image formed thereon, an high-speed image forming apparatus such as an electrophotographic image forming apparatus is often used in combination with a sheet finisher that provides finishing operations such as stapling, punching, folding and shifting. The sheet finisher is commonly equipped with a sheet stacking apparatus for stacking a plurality of sheets are stacked to form a bundle of paper.

In many cases, the sheet stacking apparatus is required to have a function of stacking sheets by aligning the edge of each sheet or a plurality of sheets being fed, in both the lateral and longitudinal directions. The sheet stacking apparatus has a sheet alignment apparatus for aligning the edges in the lateral and longitudinal directions, i.e. the edges in the conveying direction of the paper being introduced, and the edge across the width of paper.

As disclosed in the Patent Document 1, the sheet alignment apparatus includes an aligning element for aligning the lateral edge of paper by making a reciprocating motion in the direction intersecting the conveying direction when paper is introduced into the sheet stacking apparatus and a stopper for receiving the leading edge of paper when it is introduced. It aligns the paper falling from a inclined supporting table, in the lateral and longitudinal directions.

[Patent Document 1]: the Official Gazette of Japanese non-examined Patent Publication No. 10-297815.

The following describes the conventional sheet alignment apparatus with reference to FIG. 6.

The sheet alignment apparatus has a supporting table SD for supporting the sheet and aligning elements SG1 and SG2 for aligning the sheet. Sheets S are stacked on the supporting table SD. Every time the sheet S is introduced, the aligning elements SG1 and SG2 make a reciprocating motion opposite to each other in the X direction so as to align the lateral edges of the sheets S. When the stacked sheets are curled, the sheets S close to the bottom of the bundle of sheets S are formed flat due to the weight of sheets S. However, the sheets S on the upper portion are not pressed from the top, and therefore, the force for correcting the curl is reduced or the correcting force does not work, with the result that the curl of sheets S is kept uncorrected at the time of introduction.

Thus, the apparent length Lb of the sheets on the upper portion is smaller than the apparent length La of the sheets closer to the bottom. To be more specific, the sheet contour line SRS formed by connecting the edges of the sheets S is inclined with respect to the aligning line SGS drawn on the aligning face of the aligning element SG1. The spacing between the aligning line SGS and sheet contour line SRS is greater at a higher position.

As a result, alignment effects of the aligning elements SG1 and SG2 are reduced at a higher position. Thus, the alignment of the edges of sheets tends to become more difficult due to reduced alignment performances.

FIG. 6 shows an example of an upward curl wherein the central portion of sheet S is curled upward. This is the same as the downward curl wherein the central portion of sheet S is curled downward, in that the apparent length of the sheet S is smaller as the degree of curling is greater. The sheet contour line SRS is more removed from the perpendicular aligning line SGS at a higher position.

SUMMARY OF THE INVENTION

The present invention is characterized by one of the following structures:

1. A sheet alignment apparatus comprising: an aligning element for pushing edges of a sheet supported on a sheet supporting face by moving in a direction perpendicular to a conveyance direction of the sheet, thereby aligning a position of the sheet; and a driving source for reciprocating the aligning element, wherein an aligning face of the aligning element is arranged to be inclined with respect to the sheet supporting face.

2. A sheet finisher comprising: an aligning element for pushing edges of a sheet supported on a sheet supporting face by moving in a direction perpendicular to a conveyance direction of the sheet, thereby aligning a position of the sheet position; a driving source for reciprocating the aligning element; and a supporting table having the sheet supporting face being inclined by 60° or more with respect to a horizon, wherein an aligning face of the aligning element is arranged to be inclined with respect to the sheet supporting face.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall block diagram representing an image forming apparatus incorporating a sheet alignment apparatus and sheet finisher as an embodiment of the present invention;

FIG. 2 is a diagram showing the major portions of the sheet finisher as an embodiment of the present invention;

FIG. 3 is a plan of the sheet alignment apparatus as an embodiment of the present invention;

FIG. 4 is a cross sectional view showing an example of the aligning element;

FIG. 5 is a cross sectional view showing another example of the aligning element; and

FIG. 6 is a cross sectional view of a conventional aligning element.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The following describes the present invention with reference to the embodiments shown in the drawings, without the present invention being restricted thereto.

<Image Forming Apparatus>

FIG. 1 is an overall block diagram representing an image forming apparatus incorporating a sheet finisher as an embodiment of the present invention.

The image forming apparatus main body A has an image forming section GK in which a charger 2, an imagewise exposing unit 3, a developing unit 4, a transfer unit SA, a discharger SB, a separation claw 5C and a cleaning unit 6 are arranged around a photoreceptor 1. After the surface of the photoreceptor 1 has been uniformly charged by the charger 2, a latent image is formed by exposure based on the image data obtained by reading the document Ge to be copied by the light beam of the imagewise exposing unit 3 or the image data received from the outside through a network. The latent image is subjected to reversal development by the developing unit 4, whereby a toner image is formed on the surface of the photoreceptor 1.

The recording-sheet RS fed from the sheet feed tray 7A as a sheet feeding and storing unit is fed to the transfer position, where the toner image is transferred onto the recording sheet RS by the transfer unit 5A. Then the electric charge on the back side of the recording sheet RS is removed by the discharger 5B. The recording sheet RS is removed from the photoreceptor 1 by the separation claw 5C, and is conveyed by the intermediate conveyance unit 7B. Then the recording sheet RS is subjected to the process of fixing by a fixing unit 8, and is ejected by an ejection roller 7C.

When an image is formed on one side of the recording sheet RS, a conveyance path switching board 7D as one of the sheet conveyance units is switched over to the position indicated by a dotted line.

Downstream of the separation claw 5C, the remaining developer, i.e. toner is removed by the cleaning unit 6 from the surface of the photoreceptor 1 subsequent to image formation, thereby creating a required environment for next image formation.

When an image is formed on both sides of the recording sheet RS, the conveyance path switching board 7D is switched over to the position indicated by the dotted line. Then the recording sheet RS having been heated and fixed by the fixing unit 8 is conveyed downward and is switched back by the sheet reversing and conveying unit 7E so that the recording sheet RS is reversed. After that, a new toner image is transferred on the back face at the transfer position.

As will be described later, when punching, folding, binding and others operations are performed, the conveyance path switching board 7D is switched to the position indicated by the solid line, whereby the recording sheet RS having been heated and fixed by the fixing unit 8 is fed downward and is switched back by the sheet reversing and conveying unit 7E so that the recording sheet RS is reversed. After that, the sheets are fed upward with the trailing edges becoming the leading edges, and are ejected by the ejection roller 7C.

The recording sheet RS ejected from the ejection roller 7C is fed to the first sheet finisher FS1.

An operation display unit 9 capable of selecting and setting various forms of modes such as an image formation mode and sheet finishing mode is arranged on the stop front side of the image forming apparatus main body A. An image reading apparatus B as an image reading unit equipped with an automatic document conveyance apparatus G is mounted on the upper portion of the image forming apparatus main body A. The image data obtained from reading by the image reading apparatus B and the image data received from outside by facsimile machine or network communication are stored in the storage apparatus (not illustrated).

The first sheet finisher FS1 is a sheet finishing apparatus for punching and folding. The second sheet finisher FS2 is a sheet finishing apparatus for shifting and binding.

The first sheet finisher FS1 has a punching unit 12 and a folding unit 14. The recording sheet RS ejected from the image forming apparatus main body A and the cover HS supplied from the cover feed tray 11 are subjected to the process of punching and folding at the inlet. 10.

As illustrated, the folding unit 14 has several branched conveyance paths. Folding in two or folding in three can be performed by proper selection of branched conveyance paths.

A fixed ejection tray 30 used a sub-tray is arranged in the upper tray of the second sheet finisher FS2. A shifting unit 50 and ejecting unit 60 are provided along an approximately horizontal conveyance path h2. A binding unit 70 and a folding unit 80 are provided in the lower tray of the second sheet finisher FS2.

A main tray 90 for loading the shifted sheets and stapled bundles of paper is arranged on the left inside the second sheet finisher FS2. A lower tray 91 is mounted on the lower left, and folded sheets are ejected in this tray.

The following describes the structure of the second sheet finisher FS2 with reference to FIGS. 1 through 4. FIG. 2 is a diagram showing the major portions of the second sheet finisher FS2. FIG. 3 is a plan of the sheet alignment apparatus as an embodiment of the present invention, and FIG. 4 is a cross sectional view showing an example of the aligning element. In the following description, the recording sheet RS and cover HS will be collectively called the sheet S.

The sheet S ejected from the first sheet finisher FS1 is led to the inlet 20 of the second sheet finisher FS2.

A sheet branching unit composed of switching gates G1 and G2 is provided downstream of the inlet 20. Driven by a solenoid (not illustrated)., the switching gates G1 and G2 selects one of the three conveyance paths, i.e. a first conveyance path h1 for the upper tray ejection, a second conveyance path h2 for the middle tray ejection and a third conveyance path h3 for the lower tray ejection.

In the image formation on a small number of sheets, the switching gate G1 opens only the first conveyance path h1, closing the second conveyance path h2 and third conveyance path h3. The sheets S are fed along the first conveyance path h1. Gripped by the conveyance roller 31 located downstream, the sheets S go upward, and are ejected by an ejection roller 32. They are then stacked on the sub tray 30 sequentially.

The sub tray 30 has a storage capacity of accommodating a maximum of 200 sheets S.

In a large volume image formation mode where stapling is not performed, the switching gate G1 blocks the first conveyance path h1. The switching gate G2 closes the third conveyance path h3, and opens the second conveyance path h2 to allow the sheet S to be fed. Guiding the sheet S, it allows the sheet S to be ejected to the main tray 90. In the mode wherein the sheet S is ejected to the main tray 90 through the second conveyance path h2, the sheet S can be shifted by the shifting unit 50. The shifting unit 50 applies processing of shifting, whereby the ejection position of the sheet S is shifted across the width every predetermined number of sheets. The main tray 90 is lowered when a large number of sheets S are to be stacked. A maximum of 3000 sheets can be stored in the case of A4-sized or B5-sized paper.

A sheet sensor PS1 for sensing the passage of the sheet S ejected to the main tray 90 is provided in the vicinity of the ejection roller 61 constituting the ejecting unit 60.

The sheet S ejected from the first sheet finisher FS1 is fed along the third conveyance path h3 by the conveyance rollers 22 and 23. The sheet S is fed upward on the left over an intermediate stacker 71 by a stacker ejection roller 24. The trailing edge of the sheet S passes through the stacker ejection roller 24. The sheet S is detached from the stacker ejection roller 24 and is dropped onto the intermediate stacker 71 by gravity.

The intermediate stacker 71 is a supporting table for support the sheets S. A sheet supporting face of the supporting table is inclined by angle θ with respect to the horizontal line HL. To improve the performance of aligning the leading edge of the sheet S and to downsize the apparatus, the angle is preferably θ≧60°.

When the bottom edge of the sheet S has reached the stopper 72, a pair of aligning elements 73A and 73B make a reciprocating motion across the width intersecting the conveying direction of the sheet S, i.e. in the X direction, whereby the sheets S are aligned across the width (FIGS. 3 and 4). Further, the lower ends of the sheets S are aligned by the stopper 72.

The aforementioned processing is applied on a continuous basis to the sheets S supplied to the intermediate stacker 71. A predetermined number of aligned sheets S are stacked on the intermediate stacker 71.

When a predetermined number of sheets S have been stacked, the binding unit 70 operates to bind a bundle of sheets S.

When the binding has terminated, the stopper 72 is fed upward by the belt 74 driven by the motor Ml obliquely to the left in FIGS. 1 and 2, whereby the bundle of sheets S is pushed upward and is ejected to the main tray 90.

The bundle of sheets S stacked in the intermediate stacker 71 is again fed obliquely to the bottom. The sheets S are folded by the folding unit 80 and are ejected to the lower tray 91.

<Alignment of Sheet>

The alignment of sheets will be described with reference to FIGS. 2 through 5. FIG. 5 is a cross sectional view showing another example of the aligning element.

The aligning elements 73A and 73B are fixed to the belt 74 driven by the motor M2 as a driving source. They makes a reciprocating motion in the direction opposite to each other caused by the forward and reverse rotation of the motor M2, whereby the sheets S are aligned.

As shown in FIG. 4, the aligning element 73A is U-shaped, and is composed of an upper plate unit 73A1, a side plate unit 73A2 and a lower plate unit 73A3. The aligning element 73B is also U-shaped and is composed of an upper plate unit 73B1, a side plate unit 73B2 and a lower plate unit 73B3. The left side of the side plate unit 73A2 and the right side of the side plate unit 73B2 are used to align the lateral edge of the sheet S as aligning faces. The side plate unit 73A2 and side plate unit 73B2 are brought into contact with the lateral edge of the sheets S, whereby the sheets S are aligned.

The intermediate stacker 71 as a supporting table for supporting the sheet S constitutes the sheet supporting face JS that supports the sheet S. The sheets S are stacked on the intermediate stacker 71 and are loaded approximately parallel to the sheet supporting face JS. When a large number of sheets S have been loaded, the sheets S are loaded in a flat form on the lower portion by gravity, but the upper portion of the sheets is curled as illustrated. In this case, the sheets S are stacked in a curled form.

The aligning surface of the side plate unit 73A2, i.e. the left surface of the side plate unit 73A2 is formed to be deviated by an inclined angle of α1 toward the sheet from the direction PJS orthogonal to the sheet supporting face JS. The inclined angle α1 is formed along the sheet contour line SRS which is formed by a large number of curled sheets S.

The sheet contour line SRS assume varied angles depending on the degree of the curl of the sheet S. The inclined angle α1 is set to the average value of various angles or a value close thereto.

In the similar manner, the side plate unit 73B2 is formed in such a way that the aligning surface, i.e. the right side of the side plate unit 73B2 is deviated by an inclined angle of α2 toward the sheet from the direction PJS orthogonal to the sheet supporting face JS.

The inclined angles α1 and α2 are preferably 0.5° through 1.5°.

If the inclined angles α1 and α2 are smaller than 0.5°, the performance of aligning the curled paper will be reduced. If the inclined angles α1 and α2 are greater than 1.5°, then a sheet bending force will be applied to the sheets if they are flat and uncurled. This will cause the sheets to be bulged, and alignment performance will be reduced.

If the side plate units 73A2 and 73B2 are formed as described above, both curled and uncurled sheets are aligned correctly.

FIG. 5 is a cross sectional view showing another example of the aligning element.

As shown in FIG. 5, the aligning surfaces of the side plate units 73A2 and 73B2 are positioned at right angles with the sheet supporting surface JS, on the lower portion. On the upper portion, they are inclined toward the sheet S. The example shown in FIG. 5 exhibits excellent alignment performances for the curled sheets.

The aforementioned embodiments provide a sheet alignment apparatus characterized by excellent alignment performance, especially for curled sheets. This sheet alignment apparatus ensures excellent alignment of the paper, independently of the presence or absence of curling or the degree of curling.

The aforementioned embodiments provide a sheet alignment apparatus characterized by excellent alignment performance and compact structure.

The aforementioned embodiments provide a sheet finisher capable of producing a booklet characterized by preferably aligned edges of sheets.

The aforementioned embodiments allow the process of binding to be applied to the bundle of sheets with aligned edges, thereby ensuring an improved quality of bound documents. 

1. A sheet alignment apparatus comprising: (a) an aligning element for pushing edges of a sheet supported on a sheet supporting face by moving in a direction perpendicular to a conveyance direction of the sheet, thereby aligning a position of the sheet; and (b) a driving source for reciprocating the aligning element, wherein an aligning face of the aligning element is arranged to be inclined with respect to the sheet supporting face.
 2. The sheet alignment apparatus of claim 1, wherein a part of the aligning face has an acute angel with respect to the sheet supporting face on a side of the sheet.
 3. The sheet alignment apparatus of claim 1, wherein the aligning face is formed by a flat surface.
 4. The sheet alignment apparatus of claim 1, wherein the aligning face is formed by a curved surface.
 5. A sheet finisher comprising: (a) an aligning element for pushing edges of a sheet supported on a sheet supporting face by moving in a direction perpendicular to a conveyance direction of the sheet, thereby aligning a position of the sheet; (b) a driving source for reciprocating the aligning element; and (c) a supporting table having the sheet supporting face being inclined by 60° or more with respect to a horizon, wherein an aligning face of the aligning element is arranged to be inclined with respect to the sheet supporting face.
 6. The sheet finisher of claim 5, further comprising a binding unit for binding a sheet bundle on the supporting table. 